Certain conventional systems have used interferometry, laser scattering methods, or structured light for three-dimensional (3D) scanning to extract geometrical measurements, e.g., of a particular sample. Some structured light measuring systems use a quasi-static projection of light and analyze the subsequent captured images. A few of these approaches will analyze the bend or distortion in the line as a direct measure of displacement, as well as the width of the projected lines as a measure of surface curvature.
In some cases, historical approaches will use a Fourier transform of the captured image to extract the spatial frequencies of the measured surface to enable surface reconstruction. In most all cases, the historical systems use multiple line widths and pitches in the structured light to remove phase errors. However, many of these approaches could be considered static or unmodulated approaches and thus subject to higher background noise. Some of these approaches use shifting/moving light structure to enhance the signal but this is typically limited to a linear shift in one dimension.
Further, measurements of specular surfaces is a common industrial practice in the manufacturing of glass (e.g., such as that used for displays), optics, automobiles, machined metallic parts, etc. Conventional techniques are typically optical in nature due to the speed of measurement over contact techniques. However, several challenges exist to be able to measure specular parts using non-contact optical techniques. Specifically, due to their specular surfaces, optical measurements often will reflect the inhomogeneity of the light source being used; this may produce “hot spots” at specific angles of observation which undesirably result in saturation of the detector/sensor, usually resulting in either data that is not processable or erroneous results. Further, some specular material is also transparent, such as glass and or conventional optics, which results in very low signals reflected from the sample surface. Interferometers are often used to address the low signal levels and custom part handling and illumination optics are employed to reduce the issues arising from inhomogeneity of the illumination. Consequently, this generally increases unwanted cost and time, while making the system design more complicated
Embodiments according to the disclosed technology address these and other limitations.